Conventional torque converter turbines and impellers, or pumps, are typically assembled from stamped pieces. These pieces are a shell, a core and a plurality of blades for disposition between the core and the shell, for both the impeller and the turbine. The blades have tabs on opposing first and second edges. The tabs on the first edge of the turbine blades are inserted into corresponding perforations in the turbine shell. The turbine core is then placed over the tabs on the second edges of the blades. The tabs passing through both the turbine core and the turbine shell are bent over, locking the core, the shell and the blades together as an assembled turbine. The tabs on the first edge of the impeller blades are inserted into corresponding pockets in the impeller shell. Stakes are wedged into the pockets to retain the tabs. The impeller core is then placed over the tabs on the second edge of the impeller blades. The tabs passing through the impeller core are then bent over, locking the core, the shell and the blades together as an assembled impeller.
Gaps are generally present between the first edges of the blades and the shell, and between the second edges of the blades and the core. These gaps are a result of variations inherent to forming the parts by stamping. These gaps represent potential leak points or paths between the blade edges and the core and the shell. There are additional potential leak points where tabs pass through the cores or the shells, allowing fluid to escape the pump or impeller. Any such leakage reduces the efficiency of the torque converter.
The desirability of closing these gaps is well known. Sealing these gaps has the benefit of increasing the efficiency of the torque converter.
Attempts to seal these gaps have been made in the past. Brazing is one method used. The gaps are filled with molten metal. Brazing has the disadvantage of being expensive because of its time consuming nature. Another disadvantage of brazing is that the metal added to fill the gaps significantly increases the inertia of components. Brazing can also result in thermal distortion and annealing of the sheet metal parts.